Section 21B. The operation or erection of any tools, machinery or equipment, or any part thereof capable of vertical, lateral, or swinging motion; the handling or storage of any supplies, materials or apparatus or the moving of any house or other building, or any part thereof, under, over, by or near overhead high voltage lines, shall be prohibited, if at any time during such operation or other manipulation it is intended or necessary to bring such equipment, tools, materials, buildings or any part thereof within six feet of such overhead high voltage lines, except where such high voltage lines have been effectively guarded against danger from accidental contact, by either:

(1) The erection of mechanical barriers to prevent physical contact with high voltage conductors; or

(2) De-energizing the high voltage conductors and grounding where necessary. Only in the case of either of such exceptions may the six foot clearance required be reduced. The required six foot clearance shall not be provided by movement of the conductors through strains impressed by attachments or otherwise upon the structures supporting the overhead high voltage lines, nor upon any equipment, fixtures, or attachments thereon.

If neither (1) or (2) are practicable in the opinion of the utility company or other owner or operator of such overhead lines, and it is necessary to temporarily relocate the high voltage conductors, mutually agreeable arrangements shall be made with the owner or operator of such lines for their temporary relocation.

(3) In addition to (1) and (2), an insulated cagetype guard or other effective protective device of a type approved by the commissioner of labor and industries shall be installed about the boom or arm of all hoisting or other such construction equipment, except backhoes or dippers, being operated in proximity of overhead high voltage lines.

(4) All mechanical barriers and all insulated protective devices referred to herein shall be of such character and construction as are suited to work operations, and adequate for the electrical conditions to be encountered.

(5) All mechanical barriers and all insulated protective devices shall be maintained in good functioning condition and shall be subject to periodic inspection.

The provisions of this section and the preceding section, insofar as they require the erection of mechanical barriers or the de-energizing of high voltage conductors, shall not apply to the transportation of a crane, power shovel or other similar types of construction equipment upon a public way when such equipment is being transported to a construction site.